1. Field of the Invention
This invention relates to tunable solid state ultraviolet lasers, and more particularly to Ce:LiSAF solid state lasers. 2. Description of the Related Art
Continuously tunable near ultraviolet solid state lasers are desired for a number of applications, including remote sensing, and as seed sources for excimer lasers. In particular, a laser that can tune out to 308 nm and beyond is desired as a seed source for XeCl.
Solid-state lasers based on cerium-doped fluoride hosts provide a source of tunable, coherent radiation in the near ultraviolet. These fluoride hosts include YLiF.sub.4, LaF.sub.3, CaF.sub.2, and BaY.sub.2 F.sub.8. The utility of near UV cerium-doped lasers using these hosts has been limited, however, by a combination of excited state absorption, transient color center absorption, and the requirement of a high power excimer laser pump source.
In contrast to these hosts, Ce.sup.3+ -doped colquiriite crystals have absorption bands which overlap the fourth harmonic output of Nd.sup.3+ -based lasers. Accordingly, these crystals may be suitable for the same applications as the Nd.sup.3+ -based lasers.
Tunable Ce.sup.3+ :LiCaAlF.sub.6 (Ce:LiCAF) lasers have been demonstrated using a frequency-quadrupled, Q-switched Nd:YAG pump laser operating at 266 nm. However, this laser suffers from several shortcomings. The Ce:LiCAF laser has a low output power, and a low (about 8.7%) slope efficiency. Further, its tunability range has been extended only up to about 297 nm. Since the fluorescence spectrum of Ce:LiCAF does not have significant intensity at longer wavelengths, it is anticipated that the tunability of the Ce:LiCAF laser has been extended about as far as is practicable. In particular, Ce:LiCAF lasers will not be suitable for use as seed sources for XeCl.